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Underfloor heating: an architect's guide for a villa
Underfloor heating: systems, temperatures, suitable floors and nine questions for your heating engineer.
Underfloor heating: what it is and why it matters in a villa
Underfloor heating warms a house from below, with a large surface at low temperature instead of a few hot radiators. For an architect the first benefit is visible: no radiators under the glass, free walls, cleaner plans. The second is felt: the air stays still, feet are not cold, and warmth is even.
It is not a choice to make from a price per square metre, though. It works well within a coherent design of envelope, windows, floors and heat source, and badly when added to a house that leaks heat. This guide explains how to think about it, what to ask and where problems begin.
Underfloor heating: the essentials
- It runs at low temperature: water arrives at about 30–40 °C, which is why it pairs well with a heat pump.
- It needs depth: wet systems generally take at least about 10 centimetres.
- It is slow: you regulate it rather than switching it on and off.
- The surface is not hot: the right feeling is an absence of cold.
- The floor sets the output: stone and porcelain conduct, wood must be chosen with care.
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Types of underfloor heating
A guide by InfoBuild (in Italian) separates water systems, the most common, from electric ones, and wet from dry systems:
| System | How it works | When to choose it | Limit |
|---|---|---|---|
| Wet system in screed | Pipes embedded in the screed | New build or full rebuild | Inertia, about 10 cm of build-up |
| Dry water system | Prefabricated panels, no wet screed | Renovations, light floors | Reacts fast but cools fast |
| Electric | Resistance mats under the floor | Small areas, one bathroom | Used far less: depends on the cost of electricity |
In a wet system the build-up generally takes at least about 10 centimetres, with a top screed of at least 3 centimetres, preferably self-levelling and highly conductive. A dry system is much thinner, faster to lay and quicker to respond. The inertia of a screed is not an absolute flaw: in a well-insulated house it stores and releases heat steadily.
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Temperatures: the numbers to know
Underfloor heating warms with water that is barely hot:
| Parameter | Indicative value | Source |
|---|---|---|
| Flow water | about 30–40 °C, often about 35 °C | InfoBuild, Bosch |
| Surface, living zones | maximum 29 °C | Trade technical sources |
| Surface, bathrooms | about 33 °C | Trade technical sources |
| Surface, perimeter zones | maximum 35 °C | Trade technical sources |
| Water in cooling mode | about 15–18 °C | InfoBuild |
A note from the Swiss association suissetec (in Italian) gives an example: with +5 °C outside, the mean water temperature is about 28 °C and the surface about 22 °C. It also explains why people are surprised: with such low flow temperatures the floor is not noticeably warm, especially in mid-season, and you may think the system is off. That is correct operation. The surface limits come from trade technical sources citing EN 1264: we have not read the standard’s text, which your designer must apply.
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Underfloor heating and heat pumps
A heat pump performs better when it makes water that is not very hot, and a radiant floor asks for exactly that: according to Bosch Home Comfort (in Italian) flow is about 35 °C, and a reversible unit can also cool in summer. It does need careful design, the right heating curve and hydraulic balancing.
Floor cooling works with water at about 15–18 °C. Watch for condensation: air humidity must be controlled, generally with dehumidifiers or ventilation. In our Villa Edit catalogue, for heat pumps we list Daikin, Mitsubishi Electric, NIBE and Viessmann; for heat recovery ventilation Zehnder; for water treatment BWT and Culligan. We have not yet selected a maker of radiant panels and cite none: that choice belongs to the systems designer. None of these brands is a partner of this guide.
Which floors work best
The finish is part of the system. The more it resists the passage of heat, the hotter the water must be and the worse the heat pump works:
| Finish | Behaviour | What to ask |
|---|---|---|
| Stone and porcelain | Conduct well, the most suitable | Movement joints, laying, start-up times |
| Engineered wood | Suitable if stable and glued | Thermal resistance, species, room humidity |
| Floating wood | Underlay and air add resistance | Resistance of the full build-up |
| Carpet and thick rugs | Insulate and cut output | Avoid them on main areas |
For wood, the reference cited by trade sources is a maximum thermal resistance of 0.15 m²K/W for the full build-up; the maker Bauwerk names gluing as the most suitable method. Parquet suffers from changes in humidity, and a system that dries winter air can open the joints. Before you choose a wide oak board, ask the maker for its radiant floor data and start the system with a proper first-heating protocol. For stone, read our natural stone guide.
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Retrofitting underfloor heating
In an existing villa the problem is level. Doors, stairs, thresholds and ceiling heights limit the build-up, and removing the old screed can disturb pipes and floors. Dry or low-profile systems exist for this. The first check is another one, though: how much heat the house loses. If windows are old and walls uninsulated, the floor alone will not do. You would need hotter water, or accept less comfort to stay within the surface limits.
The system gives little in rooms with small floor areas and many outside walls, as suissetec notes. In those cases a bathroom may need a towel rail or a radiant wall. No pipes go under fixed units and kitchens. And the screed must dry for the right time before the finish goes down: site haste is a frequent cause of ruined floors.
Pros and cons
Pros: free walls, even warmth, less air movement, low temperature suited to heat pumps, the option of cooling. Cons: high initial cost, above all in renovations; long response times with screed; difficult repairs; risk of scale and corrosion if the water is untreated; depth to find. If you do not want a house at a steady temperature but to heat it only at weekends, think hard: a heavy screed is not made for quick starts.
We publish no price per square metre: the figures in circulation vary widely and depend on system, manifolds, heat source, screed and demolition. For a true comparison, have two contractors quote the same specification. Tax relief changes every year too, in Italy and elsewhere: check what applies with an adviser and leave it out of the sums at first.
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What changes in the architecture
Removing radiators frees more than you might think. Large windows can drop to the floor, furniture sits against walls, corridors stay clean. But comfort in front of a large window must be designed: cold glass makes the air fall, and in perimeter zones pipes are laid closer together, where trade sources allow higher surface temperatures. With high-performance windows the problem shrinks considerably.
The continuous floor is the other great consequence. One stone or one board from living room to kitchen needs well-drawn joints: they follow the circuits and must be decided with the laying pattern, not discovered on site. Fixed elements count too: kitchen islands, walk-in wardrobes, baths and fireplaces are set before the pipes go down, because you must not drill there and need no heat.
The sun is part of the system. A south-facing room gets free heat on clear winter days, and a heavy screed responds late: without zone control the room overheats. So external blinds, overhangs and sensors should be designed together. Rugs and low furniture without legs cut output: worth knowing before you choose the big rug in the living room.
Maintenance and lifespan
A well-made system asks for little attention, but not none. The water should be treated to limit scale and corrosion, manifolds checked, and the heating curve adjusted in the first winter, when you see how the house really behaves. Keep the circuit drawing with photographs from before the pour: one day, whoever drills for a piece of furniture or a service will know where the pipes run. It is a simple document, worth more than any guarantee.
The design: what to ask your heating engineer
- A room-by-room heat loss calculation.
- Pipe spacing and number of circuits per room.
- The design flow temperature on the coldest day.
- The thermal resistance of the chosen floor.
- The position of the manifolds, accessible but out of sight.
- The controls: sensors, zones, heating curve.
- Movement joints, drawn together with the floor.
- The first-heating protocol for the screed.
- Treatment of the system water.
A house with a good envelope needs few watts and allows even lower temperatures, as we explain in our passive house guide. In the bathroom, a warm floor is the natural companion of a walk in shower. And the controls count as much as the pipes: a radiant house is easy to run with few gestures if the curve is right. For an opinion on a project, ask for a preliminary reading.
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Underfloor heating: frequently asked questions
How does underfloor heating work?
Low-temperature water runs through pipes under the finish and warms the floor, which gives heat to the room by radiation.
What temperature should it run at?
Typical flow is about 30–40 °C, often about 35 °C, following the heating curve set by the engineer. You usually set the room temperature and leave it steady.
Is underfloor heating worth it?
In a well-insulated new villa with a heat pump, it usually fits very well. In a leaky house it fits badly. The decision depends on the envelope, not on the system.
What are the disadvantages?
Initial cost, the depth needed, long response times with screed, difficult repairs, the need to treat the water.
Can you put wood floors over underfloor heating?
Yes, if suitable and with limited thermal resistance: the technical reference cited is 0.15 m²K/W for the full build-up. Gluing is the most suitable method.
Can you retrofit it in an existing house?
Yes, with dry or low-profile systems, after checking levels, floors and the house’s heat loss.
Can you cool with a radiant floor?
Yes, with a reversible heat pump and water at about 15–18 °C, controlling humidity to avoid condensation.
Planning the systems of a villa?
Send us the project or the current state: we will tell you what to verify before you choose. For a complete project see Signature Architecture or write to us from the contact page.
Sources: suissetec, 2011 note (Swiss rules, used as an example); Bosch Home Comfort; InfoBuild; InfoBuild, floorings; Bauwerk. Checked on 31 October 2026. Temperature and thermal resistance limits are reported from trade technical sources: the design must refer to the standard in force. Photos: projects by Federico Cappellina Architects; they do not imply that the house shown has underfloor heating.
Would you like an opinion on the project?
Send us the project: we reply with the points to verify.
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